Rosenberg H, Gerdes R G, Chegwidden K
J Bacteriol. 1977 Aug;131(2):505-11. doi: 10.1128/jb.131.2.505-511.1977.
Mutants of Escherichia coli K-12 were constructed such that each possessed one single major system for phosphate transport. A comparison of these strains showed that one of the systems (PIT) was fully constitutive, required no binding protein, and operated in spheroplasts. It permitted the complete exchange of intracellular phosphate with extracellular phosphate (or arsenate) and was completely inhibited by uncouplers. The other system, PST, was repressible by phosphate concentrations above 1 mM, required the phosphate-binding protein for full activity, and did not operate in spheroplasts. It catalyzed very little exchange between internal and external phosphate and was resistant to uncouplers. The maximal velocities attained by the two systems were approximately the same, but the affinity for phosphate in the PST system was greater by two orders of magnitude. In strains in which both systems were fully operative, the initial rates of uptake was nearly additive, and the systems appeared to interact with a common intracellular phosphate pool.
构建了大肠杆菌K-12突变体，使每个突变体都拥有一个单一的主要磷酸盐转运系统。对这些菌株的比较表明，其中一个系统（PIT）是完全组成型的，不需要结合蛋白，并且在原生质球中起作用。它允许细胞内磷酸盐与细胞外磷酸盐（或砷酸盐）完全交换，并被解偶联剂完全抑制。另一个系统PST在磷酸盐浓度高于1 mM时可被抑制，需要磷酸盐结合蛋白才能发挥全部活性，并且不在原生质球中起作用。它催化的细胞内和细胞外磷酸盐之间的交换很少，并且对解偶联剂具有抗性。这两个系统达到的最大速度大致相同，但PST系统对磷酸盐的亲和力高两个数量级。在两个系统都完全起作用的菌株中，摄取的初始速率几乎是累加的，并且这两个系统似乎与一个共同的细胞内磷酸盐库相互作用。
